1. Field of the Invention
The present invention relates to a device for determination of parameters of particles in conductive solution and, more particularly, to a device for measuring volumes of blood cells. The present invention also relates to a microscopic hole assembly used in the device.
2. Discussion of the Related Art
In conventional technologies of detecting and analyzing blood cells, an analysis of the blood cells is one of the most commonly conducted items in medical laboratories, which is useful for diagnosis as well as differentiate diagnosis of diseases, treatment and observation, retrospective analysis and analysis of heath condition.
At present, an impedance detection method using Coulter theory is one of the main methods used by a blood analyzer for sorting and counting. An absolute majority of three-classification blood cell analyzers used home and abroad takes advantage of the Coulter theory, also called, an impedance-based microscopic hole sensor blood cells counter, such as Sysmex KX-21, Coulter AC.T diff, Nihon Kohden MEK-516K, Horiba ABX Micros 60/CT, Mindray BC-3000Plus etc.
By Coulter theory refers to measurement of particles contained in a fluid according to different impedances resultant from different volumes of particles passing through a microscopic hole. Specifically, as blood cells pertain to a relatively poor conductor, they may change the original constant impedance both inside and outside the microscopic hole when the blood cells, suspended in a conductive solution, pass through the detection microscopic hole. Therefore, changes in the impedance are detectable by a sensor established in the microscopic hole and are processed by a processing circuit to generate electric pulses. Based on the amplitude of the pulse, the cell volume may be determined, and based on the number of the pulse, the cell number may also be determined. A directly perceivable distribution graph may be drawn to reflect the above electric-pulse signals, which is processed by a corresponding processing circuit. For example, when the blood analyzer is collecting various data of the erythrocytes, leucocytes and blood platelets, the volumes thereof (transverse axis) and relative occurrence frequencies (vertical axis) are shown as a curve graph in a coordinate system, thus forming a histogram showing the blood cell distribution.
Referring to FIG. 1a, a conventional microscopic hole sensor and its equipotential lines are schematically shown. In FIG. 1a, four tracking paths PI, PII, PIII, PIV and three refluent paths RI, RII, RIII of the particles are exemplified. FIG. 1b shows a waveform diagram of the pulses generated by individual paths of the particles as shown in FIG. 1a. As can be seen from FIG. 1b, the closer the particles come to the wall of the microscopic hole, the greater disturbance occurs to the measured signals thereof. For example, the particles in the tracking path PIV generate an obvious M-shaped waveform signal, and those in the tracking path PI are given the most accurate measurement. Though a slight change happens to the measured signals of the particle in the tracking paths PII, PIII, it does not lead to a serious distortion. FIG. 1c shows signals in small fat form generated by the different paths of individual refluent particles shown in FIG. 1a. As apparent from FIG. 1c, the particles in the path RIII generate rather huge fat signals, as compared with the best-measured signals of the particles in the tracking path PI. The fat signals generated by the particles in the path RIII may adversely affect the measurement result. FIG. 1d shows an inaccurate histogram of detected particles caused by the anomalous paths and refluences. For example, the accumulated effect produced by the anomalous paths of the particles in path PIV and the refluences of the particles in the refluent path RIII leads to an accumulated distortion in the histogram of FIG. 1d. The shadowy portion in FIG. 1d represents an accumulated distortion. Therefore, the measurement result suffers from a serious distortion.
In current blood-cell analyzers, most of the counting microscopic hole sensors adopt a system structure shown in FIG. 3 and arrange the microscopic hole sensor between two liquid pools 110 and 120. Through adjusting pressures of the two liquid pools 110 and 120, e.g., applying a positive pressure to the liquid pool 110 and meanwhile applying a negative pressure to the liquid pool 120, the liquid may be measured based on the Coulter theory when the liquid is driven to flow through the microscopic hole sensor of the microscopic hole sensor assembly structure 100.
However, in the structure of the conventional microscopic hole sensor assemblies, the wall surface of the microscopic hole sensor at each liquid pool side is perpendicular to the orifice path 130 defined in the microscopic hole sensor. Consequently, due to the collecting effect of the liquid, when passing the microscopic hole sensor assembly, the liquid carrying particles may rush into the orifice path 130 or adhere to the wall surface of the orifice path 130. Therefore, unfavorable effect is produced to the measurement, such as the anomalous paths shown in FIG. 1b and the refluence shown in FIG. 1c. 
Normally, prior art counting signal of the blood cells have faults shown in FIGS. 2a to 2d, to be more specific, slow signal rise edges and steep signal fall edges shown in FIGS. 2a and 2b, undue M-shaped waves and multi-peak waves of signals shown in FIG. 2c, and undue unknown signals and serious noises shown in FIG. 2d. Therefore, U.S. Pat. No. 6,111,398 discloses a microscopic hole sensor assembly for detecting particles, which has the four configurations as shown in FIGS. 4(a) to 4(d). The assembly concerned is mainly consisting of an insulated slice 50 (made of an insulated material, such as gem, ceramic or glass) and conductive slices 52, 53 (made of metal, conductive ceramic, etc.) arranged at two sides of the insulating slice 50. The US patent also discloses features of a microscopic hole detecting device, structure and size of a microscopic hole, material of the microscopic hole, drive circuit, and so on.
The Coulter-based microscopic hole sensor assembly disclosed in the above US patent partially solves the above-mentioned problems to some extent. For example, the embodiments shown in FIGS. 4(a) to 4(d) offer an excellent solution to the cell refluence and the M-shaped wave generated by the anomalous paths. However, the introduction of rather thick fore-and-aft conductive materials 52, 53 into the Coulter microscopic hole sensor assembly increases the effective deepness of the orifice. In this way, some protein and cell fragments in the blood can easily adhere to the circumference of the microscopic hole. Consequently, in addition to an unfavorable effect on the signal quality of the cell counting pulse, a jam phenomenon may easily occur in the counting process. Therefore, the Coulter-based blood cell analyzer adopts additional expensive equipment for obviating the jam.
In a word, some conventional technologies fail to eliminate aberrance and noise of the detection signals. To solve this problem, some technologies as disclosed propose to establish conductive materials, which however have a rather strict demand on the configuration of the microscopic hole assembly. In addition, a new problem has arisen, i.e., the above jam phenomenon. As such, expensive equipment for obviating the jam must be additionally introduced therein, which enhances the production cost of the device.
Therefore, an earnest need exists to improve and develop the prior art technologies.